The Athletic reported in June that Forest and United had reached an agreement for Henderson, 25, subject to a medical.
Forest will pay Henderson’s entire salary during his season-long loan. Within the loan agreement, there is no option to purchase Henderson.
Henderson joins Forest as a direct replacement for Brice Samba, who has informed the club that he will not sign a new contract and wishes to leave this summer. His contract expires next summer. Samba is expected to join Lens if they can agree with Forest on a fee.
The England goalkeeper has already made an impression in the Premier League while on loan at Sheffield United in the 2019-20 season. However, since rejoining United, he has struggled for playing time, failing to displace first-choice goalkeeper David De Gea.
On August 6, Forest will kick off their 2022-23 Premier League season against Newcastle United.